Single carrier/ds-cdma packet transmission method, an uplink packet transmission method in a multi-carrier/ds-cdma mobile communications system, and a structure of a downlink channel in a multi-carrier/ds-cdma mobile communications system

ABSTRACT

The present invention provides a single carrier/DS-CDMA packet transmission method wherein a predetermined time slot is assigned to reservation demand packet transmission in regard to a spreading code, and the reservation demand packet and data packets are time-multiplexed for transmission. An uplink packet transmission method in a multi-carrier/DS-CDMA mobile communication system is also provided, wherein frames are set up in each communication channel of a subcarrier, time slots which are time-segments of the frames are set up further, and a mobile station spreads a packet to be transmitted by a spreading code and the information signal is transmitted to a base station in a predetermined time slot. A downlink channel configuration in a multi-carrier/DS-CDMA mobile communication system is further provided, wherein a plurality of communication channels assigned to each of a plurality of subcarriers are divided for every predetermined time frame, and multiplexed, and the plurality of the communication channels assigned to each subcarrier include a common-control channel used by a plurality of users in common, and communication channels peculiar to each user.

TECHNICAL FIELD

The present invention relates to DS-CDMA (Direct Sequence-CodeDivisional Multiple Access) mobile communications, and particularlyrelates to single carrier/DS-CDMA mobile communications andmulti-carrier/DS-CDMA mobile communications.

BACKGROUND TECHNOLOGY

Multi-carrier/DS-CDMA mobile communications and single carrier/DS-CDMAmobile communications are used as DS-CDMA mobile communications.

When data length to be transmitted is far longer than one packet lengthin a single carrier/DS-CDMA uplink packet transmission method, anefficient transmission is achieved at the time of call connection byfixedly assigning spreading codes and time slots to be used incommunication.

In this case, efficient multiplexing is necessary with respect toreservation demand packets for reserving the allocation of spreadingcodes and time slots as well as with respect to data packets fortransmitting real data. Since the probability of reservation demandpackets being able to be transmitted are not controlled in theconventional technique, collision of reservation demand packets occurfrequently at the time of heavy traffic, giving rise to a problem that atransmission efficiency decreases.

In “Performance of orthogonal CDMA codes for quasi-synchronouscommunication systems” (V. DaSilva, E. Sousa: Proc. of ICUPC' vol. 2, pp995-999, 1993), first study was made about the multi-carrier/DS-CDMAmethod.

Unlike the single carrier/DS-CDMA, which transmits a CDMA signal on onecarrier, the multi-carrier/DS-CDMA divides a radio-transmissionbandwidth, and performs parallel transmission of a CDMA signal by two ormore subcarriers.

With this provision, the speed of information transmission persubcarrier becomes low, and the speed of code spreading at whichinformation signals are spread to generate CDMA signals also becomeslow. Consequently, a chip length of the spreading code can be madelonger in the multi-carrier/DS-CDMA than in the single carrier/DS-CDMA.As the chip length is increased, the influence of synchronization errorsbetween spreading codes will be alleviated. Utilizing this feature, theabove-mentioned paper applies the multi-carrier/DS-CDMA tocommunications from mobile stations to base stations in mobilecommunications systems, and presents a method of performingquasi-synchronous transmission.

Further, a performance evaluation has been conducted on a link level ofthe multi-carrier/DS-CDMA.

“On the Performance of Multi-carrier DS CDMA Systems” (S. Kondo and L B.Milstein: IEEE Transactions on Communications, vol. 44, no. 2, pp.238-246, February 1996) demonstrates that the multi-carrier/DS-CDMAprovides better properties than the single carrier/DS-CDMA according toa performance evaluation that is conducted in the presence ofnarrow-band interference.

However, conventional studies about the multi-carrier/DS-CDMA methodhave been centered around performance evaluations on the link level, andfew studies have been made on how a mobile station should communicatewith a base station and how a control signal therefor should betransmitted when this method is applied to a mobile communicationsystem.

Furthermore, these studies have a problem in that they have been basedon the circuit switching method which always secures a communicationchannel of exclusive use from the start of transmission to its end forsignal transmission from a transmitter to a receiver as usually used inthe conventional mobile communication system.

Moreover, digital mobile communication systems (for example, a PDCsystem, a GSM system, and the like) are focused onto voice communicationservices, and the systems are designed on the basis of the circuitswitching at present. Further, although a packet transmission service isplanned also in the next-generation mobile communication system (forexample, IMT-2000), which will be introduced soon, the system design isalso based on the circuit switching. Thus, in a radio-transmissionsystem based on the circuit switching, channels for an uplink and adownlink are almost equal in number, and even if a data communication isperformed, a symmetrical channel structure of the uplink and thedownlink is used. For this reason, transmission of a control command toeach user is performed using the channel corresponding to each user.

Conversely, in multimedia mobile communications for which demand issupposed to grow in the future, communications are asymmetrical betweenthe uplink and the downlink. Accordingly, it is conceivable thatdownlink traffic accounts for most of the traffic when data isdownloaded. Also, when data is uploaded, it is conceivable that theuplink traffic accounts for most of the traffic while the downlink isrequired only for response signals. In such a case, if one channelassigned to each user is used to send each user's control command, theefficiency of data transmission becomes poor.

In recent years, the multi-carrier/DS-CDMA mobile communication systemhas been attracting attention as a mobile communication system that iscapable of high-speed data transmission. This multi-carrier/DS-CDMAmobile communication system has a problem in that no scheme has yet beenproposed about a channel structure that takes into account theabove-described asymmetry in the amount of data transmission between theuplink and the downlink in high-speed data communications directed tomultimedia or the like.

DISCLOSURE OF INVENTION

A general object of the present invention is to provide an improvedsingle carrier/DS-CDMA packet transmission method, an uplink packettransmission method in a multi-carrier/DS-CDMA mobile communicationsystem, and a downlink channel structure in a multi-carrier/DS-CDMAmobile communication system, which solve the problems of theconventional technology mentioned above.

The first object of the present invention relative to the singlecarrier/DS-CDMA packet transmission method and transmission system is toprovide multiplexing of a reservation demand packet and a data packetefficiently, to improve transmission efficiency, and further to realizea flexible bandwidth control of a channel wherein the reservation demandpacket and the data packet occupy according to changes in trafficamount.

In order to attain this object, the present invention is structured suchthat a predetermined time slot of part or all of spreading codes isassigned to reservation demand packet transmission, and the reservationdemand packet and data packet are time-multiplexed for transmission, inthe single carrier/DS-CDMA packet transmission method which carries outbandwidth expansion of an information symbol by a spreading codesequence, and carries out packet transmission using this spreading code.

Moreover, the single carrier/DS-CDMA packet transmission method whichcarries out the bandwidth expansion of the information symbol by thespreading code sequence, and carries out the packet transmission usingthis spreading code is configured such that k pieces of spreading codes,where 0<k<N and N represents the number of all spreading codes, areassigned to the reservation demand packet transmission, and thereservation demand packet and the data packet are code-multiplexed andtransmitted,

the reservation demand packet transmission admission probabilitydetermined in advance is lowered when a channel occupancy rate of thedata packet exceeds a predetermined value,

the number of the spreading codes assigned to the reservation demandpacket transmission is decreased and the number of the spreading codesassigned to the data-packet transmission is increased when the channeloccupancy rate of the data packet exceeds a predetermined value,

when the channel occupancy rate of the data packet exceeds apredetermined value, the reservation demand packet transmissionadmission probability determined in advance is first lowered, and if thechannel occupancy rate of the data packet still exceeds thepredetermined value, even after lowering the reservation demand packettransmission admission probability, then subsequently, the number of thespreading codes assigned to the reservation demand packet transmissionis decreased and the number of the spreading codes assigned to thedata-packet transmission is increased,

when the channel occupancy rate exceeds the predetermined value, firstthe number of the spreading codes assigned to the reservation demandpacket transmission is decreased, and if the channel occupancy ratestill exceeds the predetermined value, even after decreasing the numberof the spreading codes assigned to the reservation demand packettransmission, then subsequently, the reservation demand packettransmission admission probability determined in advance is lowered,

the channel occupancy rate of the data packet is measured, and thenumber of spreading codes available for the reservation demand packetand the reservation demand packet transmission admission probability aredetermined,

the number of spreading codes available for the reservation demandpacket and the transmission admission probability above-mentioned areinserted into an information channel by time-multiplexing,

a short repetition period spreading code (Short code) is used as a codeto expand the bandwidth of the reservation demand packet and the datapacket, and

as the code to expand the bandwidth of the reservation demand packet,the short repetition period spreading code (Short code) is used, and along repetition period spreading code (Long code) is used as the code toexpand the bandwidth of the data packet.

The second object of the present invention is to provide an uplinkpacket transmission method for a new multi-carrier/DS-CDMA mobilecommunication system, which can realize a packet transmission with avariable transmission speed.

In order to attain this object, the present invention relative to anuplink packet transmission method in a multi-carrier/DS-CDMA mobilecommunication system that has n subcarriers (n being a natural numbertwo or larger) is structured such that frames that are segments forevery fixed time are provided to each communication channel of theabove-mentioned subcarriers, the frame is divided into time slots with Fpieces (F being a natural number, two or larger), and a mobile stationtransmits a packet to be transmitted to a base station by spreading by aspreading code in synchronous with the timing of the above-mentionedtime slot.

Further, the uplink packet transmission method for themulti-carrier/DS-CDMA mobile communication system which has nsubcarriers is structured such that:

the above-mentioned mobile station requires an assignment of a time slotand a spreading code by transmitting a reservation demand packet to theabove-mentioned base station which assigns a time slot and a spreadingcode to the demanding mobile station, and the above-mentioned mobilestation spreads a packet by spreading the packet by the spreading codeand transmits in the time slot assigned by the above-mentioned basestation,

the above-mentioned mobile station carries out the packet transmissionthrough a random access to a time slot of one the above-mentionedcommunication channels without requesting the above-mentioned basestation for an assignment of a time slot,

transmission speed of the above-mentioned mobile station is changedaccording to a transmission volume of the packet which theabove-mentioned mobile station transmits,

the above-mentioned base station assigns k1 pieces (k1 being a naturalnumber, and k1<=F×n) of the time slot for the above-mentionedreservation demand packet transmission, and further assigns m1 pieces(m1 being a natural number, and m1<=total number of available spreadingcodes) of the spreading codes, and the above-mentioned mobile stationtransmits the reservation demand packet spread by one of the assignedspreading codes in the assigned time slot,

the above-mentioned base station changes the number of the time slots k1for the reservation demand packet transmission according to the numberof the reservation demand packets during a predetermined period from theabove-mentioned mobile station,

the above-mentioned base station changes the number of the spreadingcodes m1 for the above-mentioned reservation demand packet transmissionaccording to the number of the reservation demand packets during thepredetermined period from the above-mentioned mobile station,

the above-mentioned base station changes the number of the time slots k1for the above-mentioned reservation demand packet transmission, and thenumber of the spreading codes m1 for the above-mentioned reservationdemand packet transmission according to the number of the reservationdemand packets during the predetermined period from the above-mentionedmobile station,

the above-mentioned base station notifies a transmission limit of areservation demand packet to the above-mentioned mobile station, whenthere are numerous reservation demand packets during the predeterminedperiod from the above-mentioned mobile station, the above-mentionedmobile station transmits reservation demand packets, following thelimit,

the above-mentioned base station assigns k2 pieces (k2 being a naturalnumber and k2<=F×n) of the time slot in which packet transmission ispossible and an m2 pieces (m2 being a natural number and m2<=totalnumber of available spreading codes) of the spreading code is furtherassigned for spreading a random access packet, by the above-mentionedmobile station accessing randomly for the above-mentioned mobile stationto spread and transmit the random accessing packet by one of theassigned spreading codes in the assigned time slot,

the above-mentioned base station changes the number of the time slots k2for the above-mentioned random access packet transmission according tothe number of packets during the predetermined period from theabove-mentioned mobile station which carries out random access,

the above-mentioned base station changes the number of the spreadingcodes m2 for the above-mentioned random access packet transmissionaccording to the number of packets during the predetermined period fromthe above-mentioned mobile station which carries out random access,

the above-mentioned base station changes the number of the time slots k2for the above-mentioned random access packet transmission, and thenumber of the spreading codes m2 for the above-mentioned random accesspacket transmission according to the number of packets during thepredetermined period from the above-mentioned mobile station whichcarries out random access,

the above-mentioned base station notifies a transmission limit of arandom access packet to the above-mentioned mobile station, when thereare numerous packets during the predetermined period from theabove-mentioned mobile station which carries out random access, and theabove-mentioned mobile station performs random access following thelimit,

the above-mentioned base station assigns p (p being a natural number,and p<=the total number of available spreading codes) pieces ofspreading codes to the mobile station according to the magnitude of thetransmission volume of the above-mentioned mobile station,

the above-mentioned base station assigns a spreading code having adifferent spreading factor to the above-mentioned mobile stationaccording to the magnitude of the transmission volume of theabove-mentioned mobile station, and

the above-mentioned base station performs assignment by changing atleast two of the number of spreading codes p (p being a natural numberand p<=total number of available spreading codes), spreading codeshaving different spreading factors, the numbers of time slots q (q beinga natural number, and q<=F×n) according to the magnitude of thetransmission volume of the mobile station.

The third object of the present invention is to provide a downlinkchannel structure that is capable of efficiently transmitting controlinformation to each user in a situation where information transmissionvolumes are asymmetrical between an uplink and a downlink in amulti-carrier/DS-CDMA mobile communication system.

In order to attain this object, the present invention, relative to thestructure of the downlink channel in the multi-carrier/DS-CDMA mobilecommunication system that transmits spreading codes obtained byexpanding bandwidth of information symbols by a spreading code sequenceusing two or more subcarriers that have a predetermined frequencyinterval, is structured such that two or more communication channelsassigned to each of two or more subcarriers are divided for everypredetermined time frame, multiplexed and assigned to each subcarrier,the two or more communication channels being used by a common controlchannel for two or more users, and a communication channel peculiar toeach user.

According to the downlink channel structure in the multi-carrier/DS-CDMAmobile communication system such as above, either or both ofuser-peculiar information and common information is/are included in thecommon-control channel of each of the above-mentioned subcarriers andtransmitted, when the information is transmitted from a base station toeach user (mobile station).

Moreover, from a viewpoint that information used by each user whentransmitting information to the base station should be efficientlytransmitted to each user, the downlink of the present invention can bestructured such that information for controlling transmission of eachuser's uplink is included in the above-mentioned common-control channel.The information for controlling transmission of each user's uplink caninclude a transmission power control command to control the transmissionpower of each user (mobile station), a control command used to control acall origination, and a control command to control, for example, tocontrol frequency, code (including a spreading factor), and time to beused by each user.

Moreover, from a viewpoint that a response to information transmitted byeach user should be efficiently transmitted to each user, the structureof each downlink channel of the present invention can includeinformation relative to a response to transmission of each user's uplinkin the above-mentioned common-control channel. The information relativeto the response to transmission of each user's uplink can include, forexample, a reply signal ACK (Acknowledgement) and NACK(Non-acknowledgement) to an uplink communication.

Moreover, from a viewpoint that broadcast information to be transmittedin common to each user should be transmitted efficiently, the presentinvention can include the common broadcast information to each user inthe above-mentioned common-control channel in the structure of eachdownlink channel mentioned above. The broadcast information to each usermentioned above can include time, cell (base station) information,traffic information about the cell to which the mobile station isconnected, road traffic information, and broadcast information such asabout television and the like.

Moreover, from a viewpoint that the downlink signal should be reliablydemodulated according to a condition of a radio-transmission pathbetween the base station and the user, the present invention can includea pilot symbol used for demodulating the received signal at each user inthe above-mentioned common-control channel in the structure of eachabove-mentioned downlink channel.

Moreover, the present invention allows an assignment of a common-controlchannel to one or a plurality of code channels of part or all of theplurality of subcarriers in the structure of each above-mentioneddownlink channel.

Moreover, the present invention allows the common-control channel ineach subcarrier in the structure of each above-mentioned downlinkchannel to accommodate different kinds of information.

Moreover, the present invention allows information that is included inthe common-control channel assigned to each subcarrier to betime-multiplexed into part of each time frame in the structure of eachabove-mentioned downlink channel.

Moreover, when information included in each common-control channel needsto be time-multiplexed into part of each time frame, time-multiplexingmay be carried out with respect to the same timing portion of each timeframe of each subcarrier, or may be carried out with respect todifferent timing portions of each time frame of each subcarrier asclaimed in claim 10.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a drawing showing an example of a channel structure of thefirst embodiment.

FIG. 2 is a drawing showing another example of the channel structure.

FIG. 3 is a drawing showing an example of controlling reservation demandpacket transmission admission probability.

FIG. 4 is a drawing showing an example of assignment control of thenumber of spreading codes.

FIG. 5 is a drawing showing an example of the reservation demand packettransmission admission probability control and the assignment control ofavailable number of the spreading codes for a reservation demand packet.

FIG. 6 is a drawing showing an example of the reservation demand packettransmission admission probability control and the assignment control ofavailable number of the spreading codes for a reservation demand packetof the first embodiment.

FIG. 7 is a drawing showing a channel structure of a broadcast channelin a downlink.

FIG. 8 is a drawing showing an example in which a reservation demandpacket and a data packet are bandwidth-spread using a short repetitionperiod spreading code.

FIG. 9 is a drawing showing an example in which the reservation demandpacket is spread by the short repetition period spreading code, and thedata packet is spread by a long repetition period spreading code.

FIG. 10 is a drawing showing the first implementation of the firstembodiment.

FIG. 11 is a drawing showing the second implementation

FIG. 12 is a drawing showing the third implementation

FIG. 13 is a drawing showing the fourth implementation

FIG. 14 is a drawing showing the fifth implementation

FIG. 15 is a drawing showing an example of the channel structure of thesecond embodiment between a mobile station and a base station in themulti-carrier/DS-CDMA method.

FIG. 16 is a drawing (No. 1) showing an example of an exchange ofcontrol performed between the mobile station and the base station whentransmitting a packet from the mobile station to the base station in thesecond embodiment.

FIG. 17 is a drawing (No. 2) showing an example of an exchange ofcontrol performed between the mobile station and the base station whentransmitting a packet from the mobile station to the base station.

FIG. 18 is a drawing (No. 3) showing an example of an exchange ofcontrol performed between the mobile station and the base station whentransmitting a packet from the mobile station to the base station.

FIG. 19 is a drawing (No. 1) showing assignment of a reservation demandpacket transmission slot in the second embodiment.

FIG. 20 is a drawing (No. 2) showing assignment of the reservationdemand packet transmission slot.

FIG. 21 is a drawing (No, 3) showing assignment of the reservationdemand packet transmission slot.

FIG. 22 is a drawing (No. 4) showing assignment of the reservationdemand packet transmission slot.

FIG. 23 is a drawing (No. 5) showing assignment of the reservationdemand packet transmission slot.

FIG. 24 is a drawing showing changes of the number of time slots for thereservation demand packet transmission.

FIG. 25 is a drawing showing changes of the number of spreading codesfor the reservation demand packet transmission.

FIG. 26 is a drawing showing changes of the number of time slots, andthe number of spreading codes for the reservation demand packettransmission.

FIG. 27 is a drawing showing a transmission limit of the reservationdemand packet.

FIG. 28 is a drawing (No. 1) showing assignment of a random accesspacket transmission slot in the second embodiment.

FIG. 29 is a drawing (No. 2) showing assignment of the random accesspacket transmission slot.

FIG. 30 is a drawing (No. 3) showing assignment of the random accesspacket transmission slot.

FIG. 31 is a drawing (No. 4) showing assignment of the random accesspacket transmission slot.

FIG. 32 is a drawing (No. 5) showing assignment of the random accesspacket transmission slot.

FIG. 33 is a drawing showing changes of the number of time slots for therandom access packet transmission.

FIG. 34 is a drawing showing changes of the number of spreading codesfor the random access packet transmission.

FIG. 35 is a drawing showing changes of the number of time slots, andthe number of spreading codes for the random access packet transmission.

FIG. 36 is a drawing showing a transmission limit of the random accesspacket.

FIG. 37 is a drawing (No. 1) showing assignment of spreading codesaccording to a transmission volume.

FIG. 38 is a drawing (No. 2) showing assignment of the spreading codeaccording to the transmission volume.

FIG. 39 is a drawing showing assignment of the number of time slotsaccording to the transmission volume.

FIG. 40 is a drawing (No. 3) showing assignment of the spreading codeaccording to the transmission volume.

FIG. 41 is a drawing (No. 1) showing assignment of the time slot and aspreading code according to the transmission volume in the secondembodiment.

FIG. 42 is a drawing (No. 2) showing assignment of the time slot and aspreading code according to the transmission volume.

FIG. 43 is a drawing (No. 3) showing assignment of the time slot and aspreading code according to the transmission volume.

FIG. 44 is a block diagram showing a fundamental structure of a basestation in the third embodiment of the present invention.

FIG. 45 is a block diagram showing the first structure example of acommon-control channel generation unit in the third embodiment.

FIG. 46 is a block diagram showing the second structure example of thecommon-control channel generation unit.

FIG. 47 is a block diagram showing the third structure example of thecommon-control channel generation unit.

FIG. 48 is block diagram showing the fourth structure example of thecommon-control channel generation unit.

FIG. 49 is a drawing showing the first example a downlink channelstructure in the third embodiment.

FIG. 50 is a drawing showing the second example of the downlink channelstructure.

FIG. 51 is a drawing showing the third example of the downlink channelstructure.

FIG. 52 is a drawing showing the fourth example of the downlink channelstructure.

FIG. 53 is a drawing showing the fifth example of the downlink channelstructure.

THE BEST MODE OF THE INVENTION

In the following, embodiments of the present invention will be describedwith reference to the drawings.

The first embodiment of the present invention is an embodimentconcerning a single carrier/DS-CDMA packet transmission method.

FIG. 1 is an example of a channel structure of the first embodiment.Here, the horizontal axis and the vertical axis of each channel showtime and power, respectively. Information signal is bandwidth-spread bya high-speed spreading code sequence, and the information signal whosebandwidth is expanded is transmitted by spreading codes Code1 throughCodeN and time slots TS1 through TSM. At this occasion, a certainspecific time slot is assigned to the reservation demand packettransmission.

In FIG. 1, among the spreading codes Code1 through CodeN and the timeslots TS1 through TSM, the time slot TS1 is assigned to the reservationdemand packet transmission and the other time slots TS2 through TSM areassigned to data packets.

The assignment to the reservation demand packet may be performed to partor all of the spreading codes.

FIG. 2 is another example of the channel structure of the firstembodiment.

Here, the horizontal axis and the vertical axis of each channel showtime and power, respectively. Bandwidth expansion of the informationsymbol is carried out by the high-speed spreading code sequence, and theinformation signal of which bandwidth is expanded is transmitted by thespreading codes Code1 through CodeN and the time slots TS1 through TSM.Here, a certain specific spreading code is assigned to the reservationdemand packet transmission.

In FIG. 2, among the spreading codes Code1 through CodeN and the timeslots TS1 through TSM, the spreading codes Code1 through Codek areassigned to the reservation demand packet transmission, and the otherspreading codes Code (k+1) through CodeN are assigned to the datapackets.

FIG. 3 is an example of transmission admission probability control forreservation demand packet.

Usually, as shown in FIG. 3 (A), when a terminal (mobile station)requests to make a call, a reservation demand packet is transmitted at acertain transmission admission probability p (0<p<=1).

Here, when a channel occupancy rate of the data packets exceeds apredetermined value, the transmission admission probability is loweredto q (0<q<p), in order to avoid a collision of reservation demandpackets, as shown in FIG. 3 (B).

Thereby, the collision probability of the reservation demand packets canbe reduced and transmission efficiency can be raised.

FIG. 4 is an example of assignment control of the number of spreadingcodes available to a reservation demand packet.

Here, the horizontal axis and the vertical axis of each channel showtime and power, respectively. Bandwidth expansion of the informationsymbol is carried out by the high-speed spreading code sequence, and thespread code of which bandwidth is expanded is transmitted by thespreading codes Code1 through CodeN and the time slots TS1 through TSM.Here, a certain specific spreading code is assigned to reservationdemand packet transmission.

Usually, as shown in FIG. 4 (A), the spreading codes Code1 through Codekare assigned to the reservation demand packet transmission.

When the channel occupancy rate of the data packets exceeds apredetermined value at this time, as shown in FIG. 4 (B), transmissionefficiency can be raised by decreasing the number of the spreading codescurrently assigned to the reservation demand packet, and increasing thenumber of the spreading codes assigned to the data packets.

In FIG. 4 (B), m pieces of the spreading codes (m<k) are reassigned tothe data-packet transmission from those assigned to the reservationdemand packet transmission.

That is, transmission efficiency can be raised by using the spreadingcodes Code (k−m+1) through Codek previously assigned to the reservationdemand packet will now be used by the data packet.

FIG. 5 is an example of assignment control of the number of thespreading codes available to the reservation demand packet transmissionand the transmission probability of the reservation demand packet.

Here, the horizontal axis and the vertical axis of each channel showtime and power, respectively. Bandwidth expansion of the informationsymbol is carried out by the high-speed spreading code sequence, and thespread code of which bandwidth is expanded is transmitted by thespreading codes Code1 through CodeN and the time slots TS1 through TSM.Here, a certain specific spreading code is assigned to reservationdemand packet transmission.

Usually, as shown in FIG. 5 (A), the spreading codes Code1 through Codekare assigned to the reservation demand packet transmission. Moreover,usually, when a terminal requests to make a call, a reservation demandpacket is transmitted at a certain transmission admission probability p(0<p<=1).

In order to avoid a collision of reservation demand packets, when achannel occupancy rate of a data packet exceeds a predetermined value atthis time, the transmission admission probability q (0<q<p) for thereservation demand packet is lowered first as shown in FIG. 5 (B).

If the channel occupancy rate of the data packet still exceeds thepredetermined value, the transmission efficiency is raised by decreasingthe number of the spreading codes currently assigned to the reservationdemand packet, and increasing the number of the spreading codes assignedto a data packet, as shown in FIG. 5 (C).

In FIG. 5 (C), m pieces of the spreading codes (m<k) are reassigned tothe data packet from the reservation demand packet.

That is, transmission efficiency can be raised by the data packet usingthe spreading codes Code (k−m+1) through Codek currently assigned to thereservation demand packet.

FIG. 6 is an example of assignment control of the number of spreadingcodes available to the reservation demand packets and the reservationdemand packet transmitting probability.

Here, the horizontal axis and the vertical axis of each channel showtime and power, respectively. Bandwidth expansion of the informationsymbol is carried out by the high-speed spreading code sequence, and theinformation signal of which bandwidth is expanded is transmitted by thespreading codes Code1 through CodeN and the time slots TS1 through TSM.

Here, a certain specific spreading code is assigned to the reservationdemand packet transmission.

Usually, the spreading codes Code1 through Codek are assigned to thereservation demand packet transmission beforehand as shown in FIG. 6(A).

Moreover, usually, when a terminal requests to make a call, the terminaltransmits the reservation demand packet at a certain transmissionadmission probability p (0<p<=1).

As shown in FIG. 6 (B), when a channel occupancy rate of a data packetexceeds a predetermined value at this time, the number of the spreadingcodes currently assigned to the reservation demand packet is decreased,and the number of the spreading codes assigned to the data packet isincreased. In FIG. 6 (B), m pieces of the spreading codes (m<k) arereassigned to the data packet from the reservation demand packet.

If the channel occupancy rate of the data packet still exceeds thepredetermined value, in order to avoid the collision of reservationdemand packets, the transmission admission probability q (0<q<p) for thereservation demand packet is lowered as shown in FIG. 6 (C).

In this manner, the collision probability of the reservation demandpackets is reduced and transmission efficiency is raised.

FIG. 7 is the example of a structure of the downlink broadcast channelin the first embodiment.

Here, the horizontal axis of a channel expresses time. Information aboutthe number of spreading codes available to the reservation demand packetand the transmission admission probability is inserted into thebroadcast channel, as a reservation demand packet by time-sharing

The channel is specified by the spreading code and the time slot.

FIG. 8 shows an example of a period of the spreading code for thebandwidth expansion of the reservation demand packet and the data packetin the first embodiment

Here, both the reservation demand packet and the data packet arebandwidth-spread by a short repetition period spreading code.

FIG. 9 is another example showing periods of the spreading code for thebandwidth expansion of the reservation demand packet and data packet inthe first embodiment.

Here, the data packet is bandwidth-expanded by a long repetition periodspreading code, and the reservation demand packet is bandwidth-expandedby the short repetition period spreading code.

The first implementation of multiplexing the reservation demand packetand data-packet in the single carrier/DS-CDMA uplink packet transmissionby the first embodiment is shown in FIG. 10.

FIG. 10 (A) shows a channel structure, FIG. 10 (B) shows a normalsituation, and FIG. 10 (C) is a drawing that shows a control of thetransmission admission probability for the reservation demand packetwhen a channel occupancy rate of a data packet exceeds a predeterminedvalue.

FIG. 10 shows a control of the reservation demand packet transmissionadmission probability corresponding to FIG. 3, using the packetmultiplexing method shown in FIG. 1 and the downlink broadcast channelstructure shown in FIG. 7.

In the first implementation of the first embodiment, a certain specifictime slot is assigned to the reservation demand packet transmission. Ina situation where a terminal transmits at the reservation demand packettransmission admission probability p (0<p<=1), a base station measures achannel occupancy rate of the data packets, and when the value exceeds apredetermined value, the base station transmits a command which performsa control to lower the reservation demand packet transmission admissionprobability to q (0<q<p) by inserting the command into a downlinkbroadcast channel by the time-multiplexing.

The second implementation of multiplexing the reservation demand packetand the data-packet in the single carrier/DS-CDMA uplink packettransmission of the first embodiment is shown in FIG. 11.

FIG. 11 (A) shows a channel structure, FIG. 11 (B) shows a normalsituation, and FIG. 11 (C) is a drawing showing a reservation demandpacket transmission admission probability control when the channeloccupancy rate of the data packet exceeds a predetermined value.

FIG. 11 shows a control of the reservation demand packet transmissionadmission probability corresponding to FIG. 3, using the packetmultiplexing method shown in FIG. 2 and the downlink broadcast channelstructure shown in FIG. 7.

A certain specific spreading code is assigned to the reservation demandpacket transmission in the second implementation of the firstembodiment. In a situation where a terminal transmits at a reservationdemand packet transmission admission probability p (0<p<=1), a basestation measures a channel occupancy rate of a data packet, and when thevalue exceeds a predetermined value with, the base station transmits acommand which performs control to lower the reservation demand packettransmission admission probability to q (0<q<p) by inserting the commandinto a downlink broadcast channel by the time-multiplexing.

FIG. 12 shows the third implementation of multiplexing a reservationdemand packet and a data-packet of the first embodiment in the singlecarrier/DS-CDMA uplink packet transmission.

FIG. 12 (A) shows a channel structure, FIG. 12 (B) shows a normalsituation, and FIG. 12 (C) is a drawing showing control of the number ofassigning spreading codes for the reservation demand packet transmissionwhen a channel occupancy rate of the data packet exceeds a predeterminedvalue.

FIG. 12 shows assignment control of the number of the spreading codesavailable to the reservation demand packet corresponding to FIG. 4,using the packet multiplexing method shown in FIG. 2 and the downlinkbroadcast channel structure in FIG. 7.

In the third implementation of the first embodiment, a certain specificspreading code to reservation demand packet transmission is assigned. Ina situation where k pieces of spreading codes are assigned to thereservation demand packets, a base station-measures the channeloccupancy rate of the data packets, and when the value exceeds apredetermined value, the base station transmits a command which performscontrol to reduces the number of spreading codes assigned forreservation demand packet transmission to k−m (0<m<k) by inserting thecommand into the downlink broadcast channel by the time-multiplexing.

The fourth implementation of multiplexing the reservation demand packetand the data-packet in the single carrier/DS-CDMA uplink packettransmission by the first embodiment is shown in FIG. 13.

FIG. 13 (A) shows a channel structure, FIG. 13 (B) shows a normalsituation, FIG. 13 (C) shows the reservation demand packet transmissionadmission probability control when a channel occupancy rate of a datapacket exceeds a predetermined value, and FIG. 13 (D) shows assignmentcontrol of the number of spreading codes available to the reservationdemand packet transmission when the channel occupancy rate of the datapacket exceeds the predetermined value, even after the reservationdemand packet transmission admission probability control is carried out.

FIG. 13 shows control of the reservation demand packet transmissionadmission probability and the number of spreading codes assignable forthe reservation demand packet transmission corresponding to FIG. 5,using the packet multiplexing method shown in FIG. 2, and the downlinkbroadcast channel structure FIG. 7.

In the fourth implementation of the first embodiment, a certain specificspreading code is assigned to the reservation demand packettransmission. Where a terminal is transmitting at the reservation demandpacket transmission admission probability p (0<p<=1) and the number ofthe spreading codes standing at k, a base station measures the channeloccupancy rate of the data packet, and when the measured value exceeds apredetermined value, the base station transmits a command which performscontrol to lower the reservation demand packet transmission admissionprobability to q (0<q<p) by inserting the command into the downlinkbroadcast channel by the time-multiplexing.

When the channel occupancy rate of the data packet still exceeds thepredetermined value even after this operation is performed, the basestation transmits a command that performs control to reduce the numberof spreading codes assigned for the reservation demand packettransmission to k−m (0<m<k) by inserting the command into the downlinkbroadcast channel by the time-multiplexing.

The fifth implementation of multiplexing a data-packet and a reservationdemand packet in the single carrier/DS-CDMA uplink packet transmissionof the first embodiment is shown in FIG. 14.

FIG. 14 (A) shows a channel structure, FIG. 14 (B) shows a normalsituation, FIG. 14 (C) shows assignment control of the number ofspreading codes for the reservation demand packet transmission when achannel occupancy rate of a data packet exceeds a predetermined value,and FIG. 14 (D) is a drawing showing the reservation demand packettransmission admission probability control when the channel occupancyrate of the data packet still exceeds the predetermined value even afterthe number of spreading code assignment control for reservation demandpacket transmission has been carried out.

FIG. 14 shows the reservation demand packet transmission admissionprobability control corresponding to FIG. 6, and assignment control ofthe number of the spreading codes for the reservation demand packettransmission, using the packet multiplexing method shown in FIG. 2 andthe downlink broadcast channel structure in FIG. 7

In the fifth implementation of the first embodiment, a certain specificspreading code is assigned to the reservation demand packettransmission. While a terminal is transmitting at the reservation demandpacket transmission admission probability p (0<p<=1) and the number ofthe spreading codes for the reservation demand packet transmission beingk, a base station measures a channel occupancy rate of the data packet,and when the value exceeds a predetermined value, the base stationtransmits a command which performs assignment control to reduce thenumber of spreading codes for the reservation demand packet transmissionto k−m (0<m<k) by inserting the command into the downlink broadcastchannel by the time-multiplexing. If the channel occupancy rate of thedata packet still exceeds the predetermined value after this operationis performed, the base station transmits a command that performs controlto lower the reservation demand packet transmission admissionprobability to q (0<q<p) by inserting the command into the downlinkbroadcast channel by the time-multiplexing.

In addition, the first embodiment of the present invention is applicableto both an uplink packet transmission and a downlink packettransmission.

Moreover, in the first embodiment, when a base station determines thenumber of spreading codes available for a reservation demand packet, thebase station notifies the information thereof to a mobile station,specifying the number of spreading codes, or a specific spreading code,as a reservation demand packet channel.

Next, the second embodiment of the present invention will be described.

The second embodiment is an embodiment concerning an uplink in amulti-carrier/DS-CDMA mobile communication system.

FIG. 15 is a drawing showing an example of a channel structure between amobile station and a base station in the multi-carrier/DS-CDMA method.

A frequency bandwidth to be used is divided into n subcarriers f1-fn (nbeing a natural number of two or larger). Moreover, these subcarriersf1-fn are used by time-sharing. Therefore, frames are set up to eachsubcarrier. (A frame is a segment for every fixed time, and a framelength is set to T_(F). The frames are common to all subcarriers.)Furthermore, the frames are divided into F pieces of time slots in time(F being a natural number of two or larger) TS1-TSF (1 time-slot lengthTS=T_(F)/F).

Therefore, over all subcarriers, there are F×n pieces of the time slotsin one frame.

A mobile station transmits a packet according to the timing of this timeslot. Moreover, within the same time slot, a packet is multiplexed bythe principle of the code division (CDMA) by spreading with differentspreading codes.

Therefore, by the channel structure of FIG. 15, simultaneoustransmission of a plurality of packets, F×n×(the number of multiplexspreading codes) is attained.

In the example of FIG. 15, three packets are multiplexed by CDMA in thetime slot TS1 of the subcarrier f1.

FIG. 16 shows an example of an exchange of control performed between amobile station and a base station when packet transmission is carriedout to the base station from the mobile station.

The mobile station first transmits a reservation demand packet to thebase station, demanding an assignment of a time slot and a spreadingcode for transmitting a packet (S101). To the assignment demand from themobile station, the base station assigns a time slot on a communicationchannel, and a spreading code (S102), and notifies the result to themobile station (S103).

The mobile station spreads the packet with the assigned spreading codein the time slot assigned from the base station, and transmits (S104).

Thereby, only the mobile station which was assigned the time slot andthe spreading code can transmit by spreading the packet using theassigned spreading code in the assigned time slot.

If a large number of the time slots or a large number of the spreadingcodes are assigned, a large number of packets can be transmittedsimultaneously, making a transmission capacity large.

Moreover, even when one time slot and one spreading code are assigned,the mobile station uses the assigned spreading code and the time slotwith priority, enabling a packet transmission in a large transmissionvolume as a result, if the transmission can be done periodically andreliably until information which the mobile station is to transmit isfinished.

FIG. 17 is a drawing showing an example of an exchange of controlperformed in a mobile station and a base station when packettransmission is carried out to the base station from the mobile station.The mobile station carries out a random access to one of time slots of acommunication channel, and transmits a packet (S111).

Here, if it succeeds in transmission of a packet, the packettransmission will be ended (YES at S112). When it fails (NO at S112),the mobile station carries out a random access again to one of the timeslots on the communication channel, and transmits the packet (S111).

Thus, the method, wherein the packet transmission of the mobile stationis carried out by randomly accessing one of the time slots of thecommunication channels, without requiring a time slot assignment of theabove-mentioned base station, is suitable when carrying out a packettransmission in a small transmission volume from the mobile station tothe base station.

FIG. 18 is a drawing showing an example of an exchange of controlperformed in the mobile station and the base station for changing atransmission speed according to a volume of packet transmissions thatthe mobile station is to transmit.

When the mobile station transmits a reservation demand packet to thebase station and requires an assignment of a time slot and a spreadingcode first, the volume of the transmission is also communicated (S120).

Based on the information about the assignment demand and thetransmission volume from the mobile station, the base station assigns atime slot and a spreading code on a communication channel according tothe transmission volume of the mobile station, and notifies the resultto the mobile station (S121).

The mobile station transmits packets based on the notified result(S122).

Thereby, if the transmission volume of the packets which the mobilestation is to transmit is large, the base station will allocate a timeslot that is capable of transmitting the big transmission volume (forexample, two or more time slots) and a spreading code (for example, twoor more spreading codes, and a spreading code of a small spreadingfactor), and if the transmission volume which the mobile station needsis small, the base station will allocate a time slot and a spreadingcode accordingly.

In this manner, the base station assigns a time slot and a spreadingcode adaptively according to the transmission volume of the mobilestation.

As for the mobile station, a transmission speed according to thetransmission volume is attained.

Next, a description will follow as to how the base station assigns atime slot and a spreading code for the reservation demand packettransmission, when the mobile station transmits the reservation demandpacket to the base station.

From the mobile station to the base station, a simultaneous transmissionof a plurality of packets of F×n×(the number of multiplexing ofspreading codes) is attained as shown in FIG. 15.

In the present invention, some of these F×n×(the number of spreadingmultiplexing codes) are used for the reservation demand packettransmission.

In FIG. 19, the base station assigns arbitrary k1 pieces (k1 being anatural number, and k1<=F×n) of time slots as the reservation demandpacket transmission time slots out of the F×n pieces of time slots thatare present in one frame. Then, the mobile station spreads thereservation demand packet by one of m1 pieces (m1 being a naturalnumber, and m1<=total number of available spreading codes) of spreadingcodes determined beforehand by the base station and transmits thereservation demand packet in the time slot.

In FIG. 19, a time slot TS1 of a subcarrier f1, a time slot TS1 of asubcarrier f2, and a time-slot TS2 of a subcarrier f3 and the like areassigned as the reservation demand packet transmission time slots.

In the case of FIG. 20, an example of the channel structure is shownwherein time slots TS1 generated for every frame in all subcarriers areset up as the reservation demand packet transmission time slots (k1=n).

FIG. 20 is the case where the time slots TS1 in all the subcarriersf1-fn are set up as the reservation demand packet transmission timeslots.

In the case of FIG. 21, an example of the channel structure is shown,wherein part of the time slot TS1 is set up as the reservation demandpacket transmission time slot (k1<n) in all subcarriers. Selection ofthe k1 pieces of the time slots may be dispersedly from any subcarriers,or may be continuously.

In FIG. 21, the time slot TS1 of the subcarrier f3 is not assigned as areservation demand packet transmission time slot.

In the case of FIG. 22, an example of the channel structure is shown,wherein all the time slots of one subcarrier are set up as thereservation demand packet transmission time slots (k1=F). Here, thenumber of subcarriers that set up reservation demand packet transmissiontime slots may be two or larger.

In FIG. 22, all the time slots of the subcarrier f1 are assigned as thereservation demand packet transmission time slots.

In the case of FIG. 23, an example of the channel structure is shown,wherein some of the time slots of one subcarrier are set up as thereservation demand packet transmission time slots (k1<F). Selection ofk1 pieces of the time slots may be from dispersed time slots, orcontinuous time slots.

In FIG. 23, TS1, TS2, TS4, and the like of the subcarrier f1 areassigned as the reservation demand packet transmission time slots.

When there are numerous reservation demand packets during apredetermined period from a mobile station, a reservation demand may notbe responded. Then, according to the number of the reservation demandpackets the number of time slots, the number of spreading codes, and thelike for the reservation demand packet transmission are changed.

In the case of FIG. 24, it is a drawing showing an example of controlperformed in the base station when the base station is changing thenumber of reservation demand packet transmission time slots k1 (k1 beinga natural number, k1<=F×n) according to the number of the reservationdemand packets during a predetermined period from the mobile station.

The base station measures the number of the reservation demand packetstransmitted from the mobile station during the predetermined period(S130).

If the measuring result indicates that the number of the reservationdemand packets is larger than a certain threshold (YES in S131), thenumber of the reservation demand packet transmission slots is increased,and the position of the time slot is notified to the mobile station(S133).

If the measuring result indicates that the number of the reservationdemand packets is below the threshold (YES in S132), the number of thereservation demand packet transmission slots is decreased, and theposition of the time slot is notified to the mobile station (S134).

If the number of the reservation demand packets is not larger than thethreshold (NO in S131) and the number of the reservation demand packetsis not below the threshold (NO in S132), the number of the reservationdemand packet transmission slots is not changed.

The mobile station transmits a reservation demand packet according tothe position of the reservation demand packet transmission time slotnotified from the base station.

FIG. 25 is a drawing showing an example of control performed in the basestation when the base station changes the number m1 (m1 being a naturalnumber, and m1<=total number of available spreading codes) of thespreading codes for the reservation demand packet transmission accordingto the number of the reservation demand packets from the mobile stationduring the predetermined period.

The base station measures the number of the reservation demand packetstransmitted from the mobile station during the predetermined period(S140).

If the measuring result indicates that the number of the reservationdemand packets is larger than a certain threshold (YES in S141), thespreading code m1 for spreading a reservation demand packet isincreased, and its specification is notified to the mobile station(S143).

If the measuring result indicates that the number of the reservationdemand packets is below the threshold (YES in S142), the number m1 ofspreading codes for spreading the reservation demand packet isdecreased, and its parameter is notified to the mobile station (S144).

When the number of the reservation demand packets is not larger than thethreshold (NO in S141) and the number of the reservation demand packetsis not below the threshold (NO in S142), the spreading code forspreading the reservation demand packet is not changed.

The mobile station chooses one from the spreading codes for thereservation demand packet transmission notified from the base station,and spreads and transmits the reservation demand packet.

FIG. 26 is a drawing showing an example of control performed in the basestation when the base station changes the number of the above-mentionedreservation demand packet transmission time slots k1 (k1 being a naturalnumber, and k1<=F×n), and the number of the spreading codes for thereservation demand packet transmission m1 (m1 being a natural number,and m1<=total number of available spreading codes) according to thenumber of the reservation demand packets from the mobile station duringthe predetermined period.

The base station measures the number of the reservation demand packetstransmitted from the mobile station during the predetermined period(S150).

If the measuring result indicates that the number of the reservationdemand packets is more than a certain threshold (YES in S151), “thenumber of spreading codes m1 for spreading a reservation demand packetis increased”, “the number of reservation demand packet transmissionslots k1 is increased” or “both are increased”, and the fact is notifiedto the mobile station (S153).

If the measuring result indicates that the number of the reservationdemand packets is below the threshold (YES in S152), “the number ofspreading codes m1 for spreading a reservation demand packet isdecreased”, “the number of reservation demand packet transmission slotsk1 is decreased” or “both are decreased”, and the fact is notified tothe mobile station (S154).

When the number of the reservation demand packets is not larger than thethreshold (NO in S151) and the number of the reservation demand packetsis not below the threshold (NO in S152), “the number of spreading codesfor spreading a reservation demand packet” and “the number ofreservation demand packet transmission slots” are not changed.

The mobile station chooses one from the positions of the reservationdemand packet transmission time slots and spreading codes for thereservation demand packet transmission notified from the base stationfor spreading and transmitting a reservation demand packet.

FIG. 27 is a drawing showing an example of control performed in the basestation in the case of the base station limiting transmission of areservation demand packet from the mobile station (for example,transmission of a reservation demand packet being restrictedtemporarily) since a possibility of inaccurate transmission of areservation demand packet increases when the number of the reservationdemand packets increases, and the mobile station transmitting areservation demand packet according to the limit.

The base station measures the number of the reservation demand packetstransmitted from the mobile station during a predetermined period(S160).

If the measuring result indicates that the number of the reservationdemand packets is larger than a certain threshold with (YES in S161), atransmission limit for a reservation demand packet is made stricter thanthe current condition, and the fact is notified to the mobile station(S163).

If the measuring result indicates that the number of the reservationdemand packets is below the threshold (YES in S162), the transmissionlimit of the reservation demand packet is made looser than the currentcondition, and the fact is notified to the mobile station (S164).

If the number of the reservation demand packets is not larger than thethreshold (NO in S161) and the number of the reservation demand packetsis not below the threshold, the transmission limit is not changed (NO inS162).

For a mobile station making a random access, the base station assigns k2pieces (k2 being a natural number, and k2<=F×n) of time slots for thepacket transmission, and further assigns m2 pieces (m2 being a naturalnumber, and m2<=total number of available spreading codes) of spreadingcodes for spreading a random access packet.

The mobile station spreads the random access packet by one of theassigned spreading codes and transmits in the assigned time slot.

As shown in FIG. 28, the base station assigns arbitrary k2 pieces (k2being a natural number, and k2<=F×n) as random access packettransmission time slots out of the of the F×n time slots that arepresent in one frame. And the mobile station spreads the random accesspacket by one of the m2 pieces (m2 being a natural number, and m2<=totalnumber of available spreading codes) of spreading codes determined bythe base station beforehand and transmits in the random access packettransmission time slots.

In FIG. 28, the time slot TS1 of the subcarrier f1, the time slot TS1 ofthe subcarrier f2, and the time-slot TS2 of the subcarrier f3 and thelike are assigned as the random access packet transmission time slots.

FIG. 29 shows an example of the channel structure wherein time slots ofthe time slot TS1 in all subcarriers generated for every frame are setup as the random access packet transmission time slots (k2=n).

In FIG. 29, the time slots TS1 of all subcarriers are assigned as therandom access packet transmission time slots.

FIG. 30 shows an example of the channel structure where the time slotsof the time slot TS1 generated for every frame of some subcarriers areset up as the random access packet transmission time slots (k2<n).Selecting the k2 pieces of the time slots may be from dispersedsubcarriers, or from subcarriers adjacent each other.

In FIG. 30, the time slot TS1 of the subcarrier f3 is not assigned as arandom access packet transmission time slot.

FIG. 31 shows an example of the channel structure where all the timeslots of one subcarrier are set up as the random access packettransmission time slots (k2=F).

In FIG. 31, all the time slots of the subcarrier f1 are assigned as therandom access packet transmission time slots.

FIG. 32 shows an example of the channel structure where part of timeslots of one subcarrier are set up as the random access packettransmission time slots (k2<F).

In FIG. 32, the time slot TS1, the time slot TS2, and the time-slot TS4and the like of the subcarrier f1 are assigned as the random accesspacket transmission time slots.

Selecting the k2 pieces of time slots may be from dispersed time slots,or time slots adjacent each other.

If there are numerous random access packets during the predeterminedperiod from mobile stations, a chance may arise that communication isnot available. Then, according to the number of random access packetsduring the predetermined period, the number of random access packettransmission time slots, a spreading code, and the like are changed.

In the case of FIG. 33, it is a drawing showing an example of controlperformed in the base station when the base station changes the numberof random access packet transmission time slots k2 (k2 being a naturalnumber, and k2<=F×n) according to the number of random access packetsfrom the mobile stations during the predetermined period.

The base station measures the number of random access packetstransmitted from the mobile stations during the predetermined period(S230).

If the measuring result indicates that the number of the random accesspackets is more than a certain threshold (YES in S231), the number ofrandom access packet transmission slots is increased, and the positionof the time slot is notified to the mobile stations (S233).

If the measuring result indicates that the number of random accesspackets is below the threshold (YES in S232), the number of the randomaccess packet transmission slots is decreased, and the position of thetime slot is notified to the mobile stations (S234).

If the number of the random access packets is not more than thethreshold (NO in S231) and the number of the random access packets isnot below the threshold (NO in S232), the number of the random accesspacket transmission slots is not changed.

The mobile station transmits a random access packet according to theposition of the random access packet transmission time slot notifiedfrom the base station.

FIG. 34 is a drawing showing an example of control performed in the basestation when the base station changes the number of the spreading codesm2 (m2 being a natural number, and m2<=total number of availablespreading codes) for the random access packet transmission according tothe number of random access packets from the mobile station during thepredetermined period.

The base station measures the number of the random access packetstransmitted from the mobile stations during a predetermined period(S240).

If the measuring result indicates that the number of random accesspackets is larger than a certain threshold (YES in S241), the number ofspreading codes m2 for spreading a random access packet is increased,and its parameter is notified to the mobile station (S243).

If the measuring result indicates that the number of the random accesspackets is below the threshold (YES in S242), the number of thespreading codes m2 for spreading the random access packet is decreased,and its specification is notified to the mobile station (S244).

When the number of random access packets is not more than the threshold(NO in S241) and the number of the random access packets is not belowthe threshold (NO in S242), the number of the spreading codes forspreading the random access packet is not changed.

The mobile station chooses one from the spreading codes notified fromthe base station for the random access packet transmission, and spreadsand transmits the random access packet.

FIG. 35 is a drawing showing an example of control performed in the basestation when the base station changes the number of the above-mentionedrandom access packet transmission time slots k2 (k2 being a naturalnumber, and k2<=F×n), and the number of the spreading codes for therandom access packet transmission m2 (m2 being a natural number, andm2<=total number of available spreading codes) according to the numberof the random access packets from the mobile station during thepredetermined period.

The base station measures the number of the random access packetstransmitted from the mobile stations during the predetermined period(S250).

If the measuring result indicates that the number of the random accesspackets is larger than the threshold (YES in S251), “the number of thespreading codes for spreading the random access packet m2 is increased”or “the number of the random access packet transmission slots k2 isincreased” or “both are increased”, and the fact thereof is notified tothe mobile station (S253).

If the measuring result indicates that the number of the random accesspackets is below the threshold (YES in S252), “the number of thespreading codes for spreading the random access packet m2 is decreased”or “the number of the random access packet transmission slots k2 isdecreased” or “both are decreased”, and the fact thereof is notified tothe mobile station (S254).

If the number of the random access packets is not more than thethreshold (NO in S251) and the number of the random access packets isnot below the threshold (NO in S252), “the number of the spreading codesfor spreading the random access packet” and “the number of the randomaccess packet transmission slots” are not changed.

The mobile station chooses one from the positions of the random accesspacket transmission time slots and the spreading codes for the randomaccess packet transmission, which are notified from the base station,and spreads and transmits the random access packet.

FIG. 36 shows an example of control performed in the base station whenthe base station restricts transmission of a random access packet from amobile station (for example, transmission is restricted temporarily) andthe mobile station transmits the random access packet according to thelimit, when the number of the random access packets increases, sincethere is a possibility that transmission of the random access packetsmay not be performed accurately.

The base station measures the number of the random access packetstransmitted from the mobile station during the predetermined period(S260).

If the measuring result indicates that the number of the random accesspackets is larger than the threshold (YES in S261), a transmission limitof the random access packet is made stricter than the current condition,and the fact thereof is notified to the mobile station (S263).

If the measuring result indicates that the number of the random accesspackets below the threshold (YES in S262), the transmission limit of arandom access packet is made looser than the current condition, and thefact thereof is notified to the mobile station (S264).

The transmission limit is not changed, when the number of the randomaccess packets is not larger than the threshold (NO in S261) and thenumber of the random access packets is not below the threshold (NO inS262).

In the second embodiment of the present invention, a mobile stationchanges a transmission speed according to the magnitude of thetransmission volume of packets that the mobile station is to transmit.In the following, a mode of the change of the transmission speedaccording to the transmission volume is shown.

In FIG. 37, an example is shown wherein a mobile station 1 uses p piecesof spreading codes for packet multiplexing and transmits the packets ata transmission speed p times as fast in comparison with a transmissionspeed of a mobile station 2.

FIG. 38 is a drawing showing an example which realizes a variabletransmission speed by a base station assigning a mobile station aspreading code, spreading factor of which is changed according to thetransmission volume of the mobile station within one time slot TS of acommunication channel.

FIG. 38 shows how the transmission speed of the mobile station 1 is madeSF times as fast as compared with the mobile station 2 (a chip ratebeing the same) by using a spreading code, spreading factor of which is1/SF of the spreading code for the mobile station 2, for spreadingpackets of the mobile station 1.

FIG. 39 is a drawing showing an example which realizes a variabletransmission speed by the base station assigning arbitrary q pieces oftime slots (q being a natural number, and q<=F×n) to a mobile stationwithin one frame of a communication channel according to a transmissionvolume of the mobile station.

FIG. 40, FIG. 41, FIG. 42, and FIG. 43 describe an embodiment whereinhow the base station performs an assignment by changing at least two ofthe number of spreading codes p, a spreading factor of the spreadingcode, the number of time slots q, according to the transmission volumeof the mobile station.

In FIG. 40, the transmission speed of the mobile station 1 is set atp×SF times in comparison with the mobile station 2, by assigning themobile station 1 p pieces of spreading codes that have a 1/SF spreadingfactor of the spreading factor of the spreading code of the mobilestation 2, in addition to as described in FIG. 38

In FIG. 41, the transmission speed of the mobile station 1 is furtherset at p×q times of the mobile station 2 by assigning p spreading codesto each time slot of the mobile station 1, in addition to as describedin FIG. 39.

FIG. 42 shows an example wherein the transmission speed of the mobilestation 1 is set at q×SF times of the mobile station 2 by assigning themobile station 1 spreading codes that have a 1/SF spreading factor ofthe spreading factor of the spreading code of the mobile station 2, andfurther assigning q times as many time slots.

FIG. 43 shows an example wherein the transmission speed of the mobilestation 1 is set at p×q×SF times of the mobile station 2 by assigning qtimes as many time slot as the mobile station 2 to the mobile station 1,and further assigning p pieces of spreading codes that have a 1/SFspreading factor of the spreading factor of the spreading code of themobile station 2 in each time slot of the mobile station 1.

Next, the third embodiment of the present invention will be described.

The third embodiment is an embodiment relative to downlinks in amulti-carrier/DS-CDMA mobile communication system.

A base station transmitting information to each user with a downlinkchannel structure of the third embodiment of the present invention isconfigured as shown in FIG. 44, for example. The multi-carrier/DS-CDMAmethod is used for this base station as an access method.

In FIG. 44, this base station includes a common-control channelgeneration unit 11, user channel generation units 12 (#1) through 12(#m), a multiplexing unit 13, a multi-carrier modulation unit 14, and atransmitting unit 15. The common-control channel generation unit 11carries out bandwidth expansion of a control information symbol of eachuser according to a specific spreading code sequence, and generates aspreading code corresponding to the control information symbol. Each ofthe user channel generation units 12 (#1) through 12 (#m) carries outthe bandwidth expansion of the information symbol which is to betransmitted to each user according to the spreading code sequencecorresponding to each user, and generates the spreading codecorresponding to the information symbol.

The multiplexing unit 13 synthesizes the spread codes corresponding tothe information symbol from each user channel generation units 12(#1)-12 (#m), then the synthesized signal and the spread codescorresponding to the control information symbol from the above-mentionedcommon-control channel generation unit 11 are multiplexed according to apredetermined algorithm. The algorithm of this multiplexing can be setup arbitrarily. For example, information can be multiplexed using timemultiplexing wherein information is inserted periodically in every fixedperiod, frequency multiplexing wherein information is inserted into acertain specific subcarrier, or code multiplexing wherein multiplexingis performed by a certain specific code, or any combination thereof.

The multi-carrier modulation unit 14 modulates so that the multiplexedsignal from the multiplexing unit 13 is distributed over a plurality (npieces) of subcarrier (multi-carrier) components (the inverse discreteFourier transform: IDFT). Then, the signal containing the two or moresubcarrier components obtained in this multi-carrier modulation unit 14is transmitted to the transmitting unit 15 one by one, and theabove-mentioned signal is transmitted from this transmitting unit 15 toeach user (mobile station). A frequency interval of the subcarriers usedin the above-mentioned multi-carrier modulation unit 14 is set up at ptimes (p being a positive real number) of an updating frequency (chiprate) of each spreading code sequence used in the common-control channelgeneration unit 11 and each of the user channel generation units 12 (#1)through 12 (#m).

The above-mentioned common-control channel generation unit 11 isstructured as shown in FIG. 45.

In FIG. 45, the common-control channel generation unit 11 includes anuplink transmission-control information generation unit 20 and asynthesizing unit 60. The uplink transmission-control informationgeneration unit 20 generates information for controlling a transmissionfrom each user (mobile station), and includes a transmission powercontrol information generation unit 21, a first transmission-controlinformation generation unit 22, a second transmission-controlinformation generation unit 23, a channel allocation informationgeneration unit 24, and a synthesizing unit 25.

The transmission power control information generation unit 21 generatesa transmission power control command to perform the transmission powercontrol of an uplink of the user. The first transmission-controlinformation generation unit 22 generates control information, such asfrequency, the number of codes, a time slot, and transmitting permissionprobability of random access that are to be assigned to a random access,based on traffic information and the like. The secondtransmission-control information generation unit 23 generates controlinformation, such as frequency, the number of codes, a time slot, andtransmitting permission probability of random access that are to beassigned to a reservation demand packet, based on the trafficinformation and the like. The channel allocation information generationunit 24 generates information, such as frequency, a code (a spreadingfactor is also included), and a time slot that are assigned to a user towhom a permission of transmission is to be issued in response to areservation demand packet.

The transmission power control command from the above-mentionedtransmission power control information generation unit 21 variesaccording to a state of a communication transmission channel betweeneach user (mobile station), and serves as control information peculiarto each user. On the other hand, each control information from the firsttransmission-control information generation unit 22 and the secondtransmission-control information generation unit 23 and informationabout the channel allocation from the channel allocation informationcontrol unit 24 are pieces of information common to each user.

The synthesizing unit 25 synthesizes each information bit from thetransmission power control information generation unit 21, the firsttransmission-control information generation unit 22, the secondtransmission-control information generation unit 23, and the channelallocation information generation unit 24 according to a predeterminedalgorithm. The synthesized signal acquired in this synthesizing unit 25is outputted from the uplink transmission-control information generationunit 20 as uplink transmission control information. The controlinformation from this uplink transmission-control information generationunit 20 and other common-control information are synthesized in thesynthesizing unit 60, and the synthesized signal is outputted from thecommon-control channel generation unit 11 as information for controllingthe transmission from each user.

Here, in the above, although a description about a bandwidth expansionprocess by a spreading code has been omitted, the bandwidth expansionprocess by the spreading code sequence of the above-mentionedsynthesized signal is performed in the latter part of theabove-mentioned synthesizing unit 60, and the above-mentioned controlinformation is outputted from the common-control channel generation unit30 concerned as a spreading code as mentioned above.

Further, as shown in FIG. 46, the above-mentioned common channelgeneration unit 11 can be structured so that it includes a responseinformation generation unit 30.

In FIG. 46, the response information generation unit 30 generates theresponse information corresponding to uplink transmissions of each user,and includes user response information generation units 31 (1) through31 (m) corresponding to each user and a synthesizing unit 32. Each ofthe user response information generation units 31 (1) through 31 (m)generates response commands ACK and NACK to the uplink packet from acorresponding user. The synthesizing unit 32 synthesizes informationbits relative to the response commands from each of the user responseinformation generation units 31 (1) through 31 (m) according to apredetermined algorithm.

The synthesized signal from the synthesizing unit 32 is outputted fromthe response information generation unit 30 as response information foran uplink transmission. Here, the response information is synthesizedwith other common-control information (the control information from theuplink transmission-control information generation unit 20 shown in FIG.45 may be included) in the synthesizing unit 60.

Further, as shown in FIG. 47, the common channel generation unit 11 canbe structured such that a common broadcast information generation unit40 is included.

In FIG. 47, the common broadcast information generation unit 40 includesa time information generation unit 41, a cell information generationunit 42, a traffic information generation unit 43, a road trafficinformation generation unit 44, a broadcasting information generationunit 45, and a synthesizing unit 46. The time information generationunit 41 generates the time information indicating the absolute time. Thecell information generation unit 42 generates information such as IDinformation which specifies the cell (base station) concerned,information showing the position of the base station concerned, andinformation about base stations near the base station concerned.

The traffic information generation unit 43 generates traffic informationbased on uplink and downlink communication situations in the cell of thebase station. The road traffic information generation unit 44 generatesinformation indicating road traffic situations of roads in the area ofthe cell (base station) concerned. The broadcasting informationgeneration unit 45 generates other information, such as televisioninformation and circumference information.

Each of the information generation units 41, 42, 43, 44, and 45above-mentioned does not need to synchronize in generating theinformation. The information may be generated with different periodsaccording to the kind of the information.

Information bits generated at one or more of the information generationunits 41, 42, 43, 44, and 45 mentioned above are synthesized by thesynthesizing unit 46 according to a predetermined algorithm. Thesynthesized signal from this synthesizing unit 46 is outputted from thecommon broadcast information generation unit 40 as common broadcastinformation. Further, the common broadcast information is synthesized inthe synthesizing unit 60 with other common-control information (whichmay include either or both of the response information from the responseinformation generation unit 30 shown in FIG. 46 and the controlinformation from the uplink transmission-control information generationunit 20 as shown in FIG. 45).

Further, the common channel generation unit 11 can also be configured asshown in FIG. 48.

In FIG. 48, this common-control channel generation unit 11 includes apilot symbol generation unit 50 and a synthesizing unit 60. The pilotsymbol generation unit 50 generates a pilot symbol known to all users incommon for synchronization, channel estimation, and the like. The pilotsymbol from this pilot symbol generation unit 50 is synthesized by thesynthesizing unit 60 with other common-control information (which mayinclude at least a kind of information of the control information fromthe uplink transmission-control information generation unit 20 shown inFIG. 45, the response information from the response informationgeneration unit 30 shown in FIG. 46, and the common broadcastinformation from the common broadcast information generation unit 40shown in FIG. 47).

Structure of the downlink channel formed in the base station that isconfigured as mentioned above, and employs the multi-carrier/DS-CDMAmethod is shown in FIG. 49.

In the example shown in FIG. 49, in each time frame at a predeterminedtime, while a common-control channel is assigned to one code channel ineach of n subcarriers 1 through n, communication channels are assignedto a plurality of code channels. Each channel (a common-control channeland communication channels) in each subcarrier is distinguished by thespreading code sequences (code) used in the common-control channelgeneration unit 11 and the user channel generation units 12 (#1) through12 (#m) mentioned above.

The common-control channel includes the information generated in thecommon-control channel generation unit 11 that may include any one of orany combination of, for example, the pilot symbol (generated by thepilot symbol generation unit 50), the uplink transmission controlinformation (generated by the uplink transmission-control informationgeneration unit 20), the response information to the uplink transmission(generated by the response information generation unit 30), the commonbroadcast information (the common broadcast information generation unit40).

Information (transmission data) which should be transmitted to a user isassigned to each communication channel such that the informationgenerated in each of the user channel generation units 12 (#1)-12 (#m)is included in the corresponding communication channel.

In addition, channels of one or a plurality of the subcarriers can beassigned to each user.

In the downlink channel structure mentioned above, a common-controlchannel of each subcarrier can be arbitrarily set up as to whatinformation is included, and as to whether information is included inthe common channel of all the subcarriers.

In the following, another example of the downlink channel structure thatis similar to the example shown in FIG. 49 is described, where acommon-control channel is assigned to one code channel in each timeframe in each of the n subcarriers 1 through n, and communicationchannels are assigned to a plurality of code channels.

In the example shown in FIG. 50, information other than the pilot symbol(uplink-control information, uplink response broadcast information) isincluded in the common-control channel of a specific subcarrier (forexample, the subcarrier 1). The pilot symbol may be included in thecommon-control channel of all the subcarriers, or in the common-controlchannel of discontinuous subcarriers.

In an example shown in FIG. 51, different subcarriers are assigned tocommon-control channels according to the kind of information to beincluded. For example, the uplink-control information is included in thecommon-control channel in the subcarrier 1, the uplink responseinformation is included in the common-control channel in the subcarrier2, and the broadcast information is included in the common-controlchannel in the subcarrier n. Like the example shown in FIG. 50, thisexample also allows the pilot symbol to be included in thecommon-control channel of all the subcarriers, or in the common-controlchannel of each discontinuous subcarrier.

In an example shown in FIG. 52, any of or any combination of theabove-mentioned pilot symbol, the uplink-control information, the uplinkresponse information and the broadcast information is included in thecommon-control channel of each subcarrier, not in each whole time framebut in a predetermined time zone T. Consequently, the informationincluded in the common-control channel in each subcarrier is transmittedfor every predetermined period to the same timing.

In the example shown in FIG. 53, above-mentioned information is includedin the common-control channel in each subcarrier, not in each whole timeframe but in some time zones, like the example shown in FIG. 52. In thisexample, however, the time zones T1, T2 through Tn differ for everysubcarrier. Consequently, the information included in the common-controlchannel in each subcarrier is transmitted for every predetermined periodat different timings.

According to the downlink channel structure in the multi-carrier/DS-CDMAmobile communication system, as mentioned above, since variousinformation can be transmitted to each user by including the informationin the common-control channel that can be commonly used by all users,efficient transmission is attained compared with the case where theinformation is transmitted by an individual channel peculiar to a user.

If information (for example, the transmission power control information,the response information to each user, the channel allocationinformation, and the like) peculiar to each user is further included inthe common-control channel, the peculiar information to a plurality ofusers can be transmitted now by one common-control channel, andefficient information transmission will be attained.

In the third embodiment, in each example mentioned above, although thecommon-control channel was assigned to one code channel of allsubcarriers, the present invention is not limited to this. It ispossible to assign a control channel to one, two or more code channelsof two or more subcarriers, partly or wholly.

According to the first embodiment of the present invention, efficientmultiplexing of a reservation demand packet and a data packet isrealized by using a time slot and a spreading code in a singlecarrier/DS-CDMA uplink packet transmission method. Further by the firstembodiment, changes in traffic amount can be flexibly met also bycontrolling the number of the spreading codes available to a reservationdemand packet and the reservation demand packet transmission admissionprobability.

Moreover, the packet transmission method in the multi-carrier/DS-CDMA ofthe second embodiment of the present invention realizes time-slotreservation type packet transmission, random access type packettransmission, and packet transmission of a variable transmission speed,enabling efficient transmission of signals of various transmissionvolumes.

Further, according to the third embodiment of the present invention, anyof information peculiar to each user and information common to all userscan be included and transmitted by inserting the information into thecommon-control channel in each above-mentioned subcarrier in amulti-carrier/DS-CDMA mobile communication system when information istransmitted from a base station to each user (mobile station).Therefore, efficient transmission of control information to each user isnow available even when there is an asymmetry in transmissioninformation volumes between the uplink and the downlink in amulti-carrier/DS-CDMA mobile communication system.

1. An uplink packet transmission method in a multicarrier/DS-CDMA mobilecommunication system having n (n being a natural number equal to or morethan two) subcarriers having communication channels, comprising: settingup frames that define constant intervals in each communication channelof the subcarriers, and further setting up time slots by temporallydividing each of the frames into F pieces (F being a natural numberequal to or more than two), and spreading, in a mobile station, a packetto be transmitted with spreading codes in synchronization with a timingof the time slots, and transmitting the packet to a base station.
 2. Theuplink packet transmission method as claimed in claim 1, said mobilestation instructing said base station to assign said time slots andspreading codes by transmitting a reservation demand packet prior topacket transmission, thereby causing said base station to assign saidtime slots and spreading codes to the mobile station, and said mobilestation spreading the packet with the assigned spreading codes andtransmitting the packet via the time slots assigned by said basestation.
 3. The uplink packet transmission method as claimed in claim 1,wherein said mobile station randomly accesses one of the time slots totransmit said packet, without instructing the base station to assignsaid time slots.
 4. The uplink packet transmission method as claimed inclaim 1, wherein said mobile station changes transmission speedaccording to a packet transmission volume.
 5. The uplink packettransmission method as claimed in claim 2, further comprising: receivingfrom said base station k1 (k1 being a natural number, and k1<F) timeslots for transmitting the reservation demand packet, and m1 (m1 being anatural number, m1<a total number of available spreading codes)spreading codes for spreading the reservation demand packet, andspreading and transmitting the reservation demand packet by one of theassigned spreading codes in at least one of the assigned time slots. 6.The uplink packet transmission method as claimed in claim 5, furthercomprising: receiving an indication that the number k1 is changed bysaid base station according to a number of reservation demand packetssent from the mobile station during a predetermined period.
 7. Theuplink packet transmission method as claimed in claim 5, furthercomprising: receiving an indication that the number m1 is changed bysaid base station according to a number of reservation demand packetssent from the mobile station during a predetermined period.
 8. Theuplink packet transmission method as claimed in claim 5, furthercomprising: receiving an indication that the number k1 and the number m1is changed by said base station according to a number of reservationdemand packets sent from the mobile station during a predeterminedperiod.
 9. The uplink packet transmission method as claimed in claim 5further comprising: receiving from the base station a packettransmission limit when plural reservation demand packets are sent fromthe mobile station during a predetermined period, and transmitting thereservation demand packets according to the transmission limit.
 10. Theuplink packet transmission method as claimed in claim 3, furthercomprising: receiving from base station k2 (k2 being a natural number,and k2<F) time slots for random access packet transmission, and m2 (m2being a natural number, and m2<a total number of available spreadingcodes) spreading codes for spreading a random access packet, andspreading a random access packet by one of the assigned spreading codesand transmitting the packet in the assigned time slots.
 11. The uplinkpacket transmission method as claimed in claim 10, further comprising:receiving an indication that the base station has changed the number k2according to a number of random access packets sent from the mobilestation during a predetermined period.
 12. The uplink packettransmission method as claimed in claim 10, further comprising:receiving an indication that the number m2 is changed by the basestation according to a number of random access packets sent from themobile station during a predetermined period.
 13. The uplink packettransmission method as claimed in claim 10, further comprising:receiving an indication that the number k2 and the number m2 is changedby the base station according to a number of random access packets sentfrom the mobile station during a predetermined period.
 14. The uplinkpacket transmission method as claimed in claim 10, further comprising:receiving from the base station a random access packet transmissionlimit when plural random access packets are sent by the mobile stationduring a predetermined period, and transmitting random access packetsaccording to the transmission limit.
 15. The uplink packet transmissionmethod as claimed in claim 4, further comprising: receiving from thebase station p spreading codes (p being a natural number, and p<a totalnumber of available spreading codes) according to the packettransmission volume.
 16. The uplink packet transmission method asclaimed in claim 4, further comprising: receiving from the base stationa spreading code having a spreading factor that varies according to thepacket transmission volume.
 17. The uplink packet transmission method asclaimed in claim 4, further comprising: receiving from the base stationq time slots (q being a natural number, and q<F) according to the packettransmission volume.
 18. The uplink packet transmission method asclaimed in claim 4, further comprising: receiving from the base stationindication that the base station has changed at least two of number p ofspreading codes (p being a natural number, and p≦a total number ofavailable spreading codes), having different spreading factors, and anumber q of time slots q (q being a natural number and q≦F) according tothe packet transmission volume.